Polymers are substances composed of very large molecules formed by linking together structural units, called monomers, in long chains. Because of their "linked" nature, polymers present significant material handling and processing problems. Mechanically- and thermally- induced stresses may act to break, or "degrade," the polymer chains, thus adversely affecting the properties of the polymer. Such problems may occur during physical contact of polymer solutions with conduit walls, valve seats and stems, and the like, during pumping through conduits, or may occur when batches of polymer are stored or shipped, and undergo physical shocks or extreme changes in ambient temperature. It has also been found that dilution of polymer solutions may, in itself, induce degradation where the difference in viscosity between the diluent and the polymer solution is appreciable at the point of diluent addition. One group of polymers susceptible to degradation during dilution is the polyacrylamides, especially partially hydrolyzed polyacrylamides. The problem is particularly troublesome where the partially hydrolyzed polyacrylamides are employed as drive fluids or mobility control agents in the secondary or tertiary recovery of oil from oil-bearing subterranean formations. Degradation of polyacrylamides of this type during dilution results in a loss of the injectivity and mobility control properties of the polymer thereby greatly diminishing the ability of the polymer to meet the performance demands of the oil-bearing formation.
Various attempts have been made to overcome the problems encountered in the handling and processing of polymer solutions. In U.S. Pat. No. 3,034,526, for example, a three-dimensional cascade system is disclosed for use in limiting degradation of such linear polymers as nylon and Saran. U.S. Pat. No. 3,468,322 discloses the use of lengths of chain in a polymer flow system to minimize shear forces created when water-soluble polymers are diluted.
Control of disruptive shear forces is the subject of U.S. Pat. No. 3,945,402 wherein specially shaped, smooth-wall conduits are used to enable flow at high Reynolds numbers.
Controlling residence time of polymers flowing through pipelines is the subject of U.S. Pat. Nos. 3,128,794 and 3,353,564. U.S. Pat. No. 3,128,794 teaches the use of diverters to direct the flow of polymer from the walls of the conduit to the center, and vice versa. U.S. Pat. No. 3,353,564 shows the utilization of screens placed in the polymer flow path to equalize residence time within the conduit and minimize thermal degradation of the polymer.